Amplification of deoxyribonucleic acid (DNA) may be carried out through use of cell-based processes, such as by culture of bacteria propagating a DNA to be amplified in fermenters. Cell-free enzymatic processes for amplification of DNA from a starting template have also been described, including the polymerase chain reaction and strand-displacement reactions.
In the past, amplification of DNA on a test scale has been performed using apparatus based on microtitre plates and robotically controlled pipettes to add reaction components as required. Such apparatus and processes are suitable for manufacturing small quantities of DNA molecules for test purposes but do not provide sufficient quantities for other purposes. Large scale amplification and manufacture of specific nucleic acids and proteins has mostly been carried out through cell-based processes. Such methods are generally effective for production of very large volumes of product but costly to set up.
There are also many apparatus available that are specifically adapted to amplify DNA samples using the thermocyclic method to effect the polymerase chain reaction (PCR). These apparatus are ideally suited to that reaction but are inflexible and cannot be adapted to perform other reactions. An example of such an apparatus is disclosed in U.S. Pat. No. 8,163,489.
Large-scale DNA synthesis using chemical synthesis, such as phosphoramidite methods, are known, but are not without drawbacks. The reaction must generally be performed in organic solvents, many of which are toxic or otherwise hazardous. Another drawback to chemical synthesis is that it is not completely efficient, since following each nucleotide addition, at least 2 percent of the growing oligonucleotide chains are capped, resulting in a yield loss. The total yield loss for the nucleotide chain being synthesised thus increases with each nucleotide added to the sequence. This inherent inefficiency in chemical synthesis of oligonucleotides ultimately limits the length of oligonucleotide that can be efficiently produced to oligonucleotides having 50 nucleic acid residues or less.
To date, biological catalysts such as polymerase have not been routinely exploited for industrial scale manufacture of DNA products and reactions have largely been limited to volumes at microliter scale. Scaling up processes using enzymatic synthesis of DNA has proved problematic, not least with the disappointing yield of DNA product.
There is therefore a need for a process that can be used to synthesise DNA and like molecules at significant scale.